Aortic valve stent graft

ABSTRACT

An implantable endoluminal prosthesis for replacing a damaged aortic valve is provided. In one embodiment, the prosthesis includes a balloon-expandable stent, a tubular conduit that extends into the ascending aorta, and a self-expanding stent. The tubular conduit extends across the balloon-expandable stent. The tubular conduit includes an artificial valve. The self-expanding stent extends across the tubular conduit into the ascending aorta. The balloon-expandable stent, the tubular conduit, and the self-expanding stent are coupled to provide unidirectional flow of fluid into the aorta and further into the coronary arteries. Also provided is a method for implanting the endoluminal prosthesis.

PRIORITY CLAIM

This invention claims the benefit of priority of U.S. ProvisionalApplication Ser. No. 60/986,908, entitled “Aortic Valve Stent Graft,”filed Nov. 9, 2007, the disclosure of which is hereby incorporated byreference in its entirety.

BACKGROUND

The present embodiments relate to implantable medical devices andmethods, and more particularly to an implantable medical device for therepair of a damaged endoluminal valve, such as an aortic valve, and amethod for implanting the same.

The aortic valve functions as a one-way valve between the heart and therest of the body. Blood is pumped from the left ventricle of the heart,through the aortic valve, and into the aorta, which in turn suppliesblood to the body. Between heart contractions the aortic valve closes,preventing blood from flowing backwards into the heart.

Damage to the aortic valve can occur from a congenital defect, thenatural aging process, and from infection or scarring. Over time,calcium may build up around the aortic valve causing the valve not toopen and close properly. Certain types of damage may cause the valve to“leak,” resulting in “aortic insufficiency” or “aortic regurgitation.”Aortic regurgitation causes extra workload for the heart, and canultimately result in weakening of the heart muscle and eventual heartfailure.

After the aortic valve becomes sufficiently damaged, the valve may needto be replaced to prevent heart failure and death. One current approachinvolves the use of a balloon-expandable stent to place an artificialvalve at the site of the defective aortic valve. Another currentapproach involves the positioning of an artificial valve at the site ofthe aortic valve using a self-expanding stent. However, these techniquesare imperfect. The normal aortic valve functions well because it issuspended from above through its attachment to the walls of the coronarysinus in between the coronary orifices, and it has leaflets of theperfect size and shape to fill the space in the annulus. These featuresare difficult to replicate in a percutaneously implanted prostheticvalve. The size of the implantation site depends on the unpredictableeffects of the balloon dilation of a heavily calcified native valve andits annulus. Balloon dilation can lead to poor valve function with apersistent gradient or regurgitation through the valve. The diameter ofthe aortic valve is small and thus the diameter of the dilation is notalways predictable, especially with a self-expanding stent. In addition,the shape of the aortic valve is not circular, which can also lead toregurgitation outside the valve.

SUMMARY

The present embodiments provide an endoluminal prosthesis for replacingan aortic valve in a subject. In one embodiment, the prosthesiscomprises a first stent, a tubular conduit, and a second stent. Thetubular conduit may comprise a valve, wherein at least a portion of thetubular conduit overlaps at least a portion of the first stent. Further,the second stent overlaps at least a portion of the tubular conduit. Inuse, ones of the first stent, the tubular conduit, and the second stentare coaxially arranged for unidirectionally passing fluid through theprosthesis.

In one embodiment, the first stent comprises a balloon-expandable stentand the second stent comprises a self-expanding stent. Theself-expanding stent may at least partially surround the tubularconduit, and the tubular conduit may at least partially surround theballoon-expandable stent. Alternatively, both the balloon-expandablestent and the self-expanding stent may at least partially surround thetubular conduit. The valve may comprise an artificial valve, which maybe located at the distal end of the tubular conduit.

In one exemplary method of operation, an endoluminal prosthesis may beintroduced into the vascular system. The endoluminal prosthesiscomprises a first stent, a tubular conduit comprising a valve, and asecond stent, wherein at least a portion of the tubular conduit overlapsat least a portion of the first stent, and at least a portion of thetubular conduit overlaps at least a portion of the second stent. Theprosthesis is advanced within the vascular system towards an aorticannulus. Then, at least a portion of the prosthesis is expanded intoengagement with the aortic annulus.

The first stent, the tubular conduit and the second stent may beadvanced into the vascular system in a sequential manner orsimultaneously. In operation, the first stent, the tubular conduit andthe second stent may be configured for unidirectionally passing fluidthrough the prosthesis and substantially or completely inhibitingretrograde flow through the prosthesis.

Other systems, methods, features and advantages of the invention willbe, or will become, apparent to one with skill in the art uponexamination of the following figures and detailed description. It isintended that all such additional systems, methods, features andadvantages be within the scope of the invention, and be encompassed bythe following claims.

DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the followingdrawings and description. The components in the figures are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention. Moreover, in the figures, likereferenced numerals designate corresponding parts throughout thedifferent views.

FIG. 1 is a partial cutaway view of a heart and an aorta.

FIG. 2 is a cutaway side view of an endoluminal prosthesis.

FIG. 3 is a top plan view of the prosthesis of FIG. 2.

FIG. 4 is a bottom plan view of the prosthesis of FIG. 2.

FIG. 5 is a partial cutaway view of an aorta with an implantedprosthesis.

FIG. 6 is another partial cutaway view of an aorta with an implantedprosthesis.

FIG. 7 is an illustration of a braided stent.

FIG. 8 is a top plan view of one embodiment of a barb attached to astent.

FIG. 9 is a perspective view of the barb attached to a stent of FIG. 8.

FIG. 10 is a side view of one embodiment of a barb.

FIG. 11 is a side view of a portion of a stent with a ring of barbspointing out from each apex.

FIGS. 12A-12B illustrate one embodiment of an artificial valve duringdiastole and systole, respectively.

FIGS. 13A-13B are a side view and top view, respectively, of oneembodiment of a supportive frame for an artificial valve.

FIG. 14 is an illustration of one example of an artificial valve with asupportive frame.

FIG. 15 is an illustration of another example of an artificial valvewith a supportive frame.

FIG. 16 is a perspective view of selected segments of a deploymentdevice with an aortic stent graft partially deployed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the present application, the term “proximal” refers to a directionthat is generally closest to the heart during a medical procedure, whilethe term “distal” refers to a direction that is furthest from the heartduring a medical procedure.

FIG. 1 shows a partial cut-away view of a heart 102 and an aorta 104.The heart 102 may comprise an aortic valve 106 that does not sealproperly. This defect of the aortic valve 106 allows blood to flow fromthe aorta 104 back into the left ventricle 108, leading to a disorderknown as aortic regurgitation. A bicuspid mitral valve 110 generallyprevents blood from flowing further backwards into the left atrium. Alsoshown in FIG. 1 are a brachiocephalic trunk 112, a left common carotidartery 114, a left subclavian artery 116, and a right ventricle 120. Aportion of the aorta 104 referred to herein as an ascending aorta 118 isshown located between the aortic valve 106 and the brachiocephalic trunk112.

FIG. 2 illustrates a first embodiment of a prosthetic device in the formof an aortic stent graft 202. In this embodiment, the aortic stent graft202 comprises three generally tubular members arranged in coaxialconfiguration, comprising from inside to outside: a balloon-expandablestent 204, a conduit 206, and a self-expanding stent 208. The conduit206 includes an artificial valve 210. The artificial valve 210 is shownin an open configuration, allowing unidirectional blood flow through theprosthesis, in the direction indicated by an arrow 240. In thisembodiment, the conduit 206 is shown as a thin walled conduit. Also inthis embodiment, the artificial valve 210 is shown near a distal end ofthe conduit 206.

The shape, size, and dimensions of each of the members of the prostheticdevice 202 may vary. Consequently, the overall size and shape of theaortic stent graft prosthesis may vary. The size of a preferredprosthetic device is determined primarily by the diameter of the vessellumen (preferably for a healthy valve/lumen combination) at the intendedimplant site, as well as the desired length of the overall stent andvalve device. Thus, an initial assessment of the location of the naturalaortic valve in the patient is determinative of several aspects of theprosthetic design. For example, the location of the natural aortic valvein the patient will determine the dimensions of the stents and thetubular conduit, the type of valve material selected, and the size ofdeployment vehicle. The length of the self-expanding stent 208 issufficient enough to overlap with the conduit 206 and extend toengagement with the ascending aorta 118.

In the embodiment shown in FIG. 2, the conduit 206 is shown ascompletely covering the length of the balloon-expandable stent 204.However, in some embodiments the conduit 206 may only partially coverthe length of the balloon-expandable stent 204. What is essential isthat the length of the conduit 206 is sufficient to overlap at least apart of the balloon-expandable stent 204, to thereby provide couplingthat provides flow of fluid through the prosthesis. Similarly, thelength of the self-expanding stent 208 can vary. What is essential isthat the length of the self-expanding stent 208 is sufficient to overlapthe conduit 206, to thereby provide coupling that provides flow of fluidthrough the prosthesis.

The tubular members are preferably axially uniform. Furthermore, thetubular members shown in FIG. 2 are presented as roughly cylindrical. Inalternative embodiments, one or more of these tubular members may becontoured. For example, one or more of the members may be graduallytapering, i.e., they may be tubular gradually narrowing distally ortubular gradually widening distally. The tubular members may further beelliptical, conical, or have combinations of regular shapes or irregularshapes that conform to the shape of the recipient's anatomy.

FIG. 3 is a top plan view of the prosthesis of FIG. 2, showing theartificial valve 210 in a closed position. In this view, the artificialvalve 210 can be seen as attached to the conduit 206. The artificialvalve 210 shown in this example includes three leaflets. Also shown inFIG. 3 is the self-expanding stent 208. As can be seen in FIG. 3, thetubular members are presented as coaxial and as roughly cylindrical. Asdescribed above, and in alternative embodiments, one or more of thesetubular members may be contoured, tapered, conical, or have irregularshapes that conform to the shape of the lumen.

FIG. 4 is a bottom plan view of the prosthesis of FIG. 2, showing theartificial valve 210 in a closed position. In addition to the conduit206 and the self-expanding stent 208, this view shows theballoon-expandable stent 204, which is the innermost member.

The prosthesis of the present embodiments may be introduced and deployedin a subject's vascular system so that it reaches the aortic annulus, asshown in FIGS. 5 and 6. Preferably, the prosthesis has a compressedstate for delivery and an expanded state upon deployment within theartery. Once the prosthesis is deployed and implanted at the site of theaortic annulus, the artificial valve of the prosthesis functionallyreplaces the aortic valve of the subject. Note the different embodimentsof an implanted prosthesis shown in FIGS. 5 and 6. In FIG. 5, theself-expanding stent 208 at least partially surrounds the tubularconduit 206, and the tubular conduit 206 at least partially surroundsthe balloon-expandable stent 204. In FIG. 6, both the balloon-expandablestent 204 and the self-expanding stent 208 at least partially surroundthe tubular conduit 206. In both embodiments, the prosthesis allowsunidirectional flow of fluid from the heart into the aorta.

Introduction and deployment of the members that comprise the prosthesiscan be simultaneous. In this situation, each of the components may bemounted on a balloon catheter. The balloon is aligned with the aorticannulus, then expanded to substantially simultaneously dilate the aorticannulus and deploy the balloon expandable stent 204 and remainder of theprosthesis. By substantially simultaneously deploying each component ofthe prosthesis at the same time the annulus is dilated, potentiallyfatal regurgitation problems may be avoided.

Alternatively, introduction and deployment of the individual members canbe sequential. If sequential deployment of the components is provided, aphysician may need to stop blood flow due to potentially fatal aorticregurgitation problems associated with dilation of the aortic annulusand subsequent individual insertion of the prosthetic components.

In a further alternative embodiment, the deployment can be a combinationof simultaneous and sequential, i.e. some members of the prosthesis canbe deployed simultaneously, whereas other or others can be deployedsequentially.

The self-expanding stent 208 included in the prosthesis may be amodified Gianturco “Z stent” or any other form of self-expanding stent.The Z-stent design is preferred for straight sections of the aorta, asit provides both significant radial force as well as longitudinalsupport.

In certain preferred embodiments, the self-expanding stent 208 can be abraided stent, as illustrated in FIGS. 6 and 7. A long, open mesh stentas depicted in FIGS. 6 and 7 provides the necessary downstream supportwithout the struts that would be required were the valve to be supportedvia annular attachment alone. The design of this stent requiresflexibility, resistance to compressive loading, and an atraumaticinterface with the aorta. The self-expanding stent may have two zones,i.e., a lower (proximal) zone of narrow diameter and fixed length(resistance to compression), and an upper (distal) zone of widerdiameter and variable length (flexibility). A braided stent, such as aWallstent, may comprise two such zones by varying the braid angle. Ifthe stent were made of Nitinol, its exact braid shape could bedetermined by heat setting after the wires had all been bent and joinedinto the basic shape. The proximal end of the stent can be made moreatraumatic by joining the ends of the wires as loops.

Typically, the prosthesis has a circular cross-section when fullyexpanded, so as to conform to the generally circular cross-section of ablood vessel lumen. In one example, the balloon expandable stent 204 andthe self-expanding stent 208 may include struts and acute bends orapices that are arranged in a zigzag configuration in which the strutsare set at angles to each other and are connected by the acute bends.The stents may include a curved or hooped portion. The presentembodiments can be used with a wide variety of stents, including, butnot limited to, shape memory alloy stents, expandable stents, and stentsformed in situ. Any stent shape suitable for expansion to fit thepertinent anatomical space may be used.

Preferably, the self-expanding stent 208 is formed from nitinol,stainless steel, or elgiloy. Examples of other materials that may beused to form stents include: carbon or carbon fiber, tantalum, titanium,gold, platinum, inconel, iridium, silver, tungsten, cobalt, chromium,cellulose acetate, cellulose nitrate, silicone, polyethyleneteraphthalate, polyurethane, polyamide, polyester, polyorthoester,polyanhydride, polyether sulfone, polycarbonate, polypropylene, highmolecular weight polyethylene, polytetrafluoroethylene, or anotherbiocompatible polymeric material, or mixtures or copolymers of these;polylactic acid, polyglycolic acid or copolymers thereof; apolyanhydride, polycaprolactone, or polyhydroxybutyrate valerate. Stillother biocompatible metals, alloys, or other biodegradable polymers ormixtures or copolymers may be used.

The aortic stent graft 202 may include a biocompatible graft materialattached to at least a portion of any stent. The graft material may beconnected to the artificial valve. In one embodiment, the graft materialforms a lumen, which lumen is adapted to seal against the wall of theaorta at a site proximal to the aortic annulus. In this embodiment, theblood flows through the lumen of the stent graft and the artificialvalve regulates the unidirectional flow of blood through the prosthesis.

The biocompatible graft material is preferably non-porous so that itdoes not leak under physiologic forces. The graft material is preferablymade of woven DACRON® polyester (VASCUTEK® Ltd., Renfrewshire, Scotland,UK). Preferably, the graft material is formed without seams. The tubulargraft can be made of any other at least substantially biocompatiblematerial including such fabrics as other polyester fabrics,polytetrafluoroethylene (PTFE), expanded PTFE, and other syntheticmaterials. Naturally occurring biomaterials, such as collagen, are alsohighly desirable, particularly a derived collagen material known asextracellular matrix (ECM), such as small intestinal submucosa (SIS). Anelement of elasticity may be incorporated as a property of the fabric orby subsequent treatments such as crimping. The dimensions of the graftmay vary according to the dimensions of the artery that is treated. Foreach patient, a graft can be selected that has diameters that exceedthose of the recipient artery. The stent is relied upon to exertsufficient radial outward force to effect a seal between the graftmaterial and the inner wall of the aorta.

To anchor the aortic stent graft to the wall of the arterial lumen,attachment systems are preferably included on the balloon-expandablestent 204 and/or the self-expanding stent 208. The preferred attachmentsystem includes arterial wall engaging members, for example protrusionsor barbs 230, as shown in FIGS. 2-4, 8-11, and 16.

Preferably, sharp metal barbs 230 project outward from the surface ofthe prosthesis 202. Barbs 230 can be attached to one or more members ofthe prosthesis 202. In one embodiment, barbs 230 are attached to theself-expanding stent 208. In another embodiment, barbs 230 are attachedto a balloon-expandable stent 204. Yet in another embodiment, barbs 230are attached to both the self-expanding stent 208 and theballoon-expandable stent 204. The barbs 230 point caudally, cranially,or in both directions. The barbs 230 are soldered, brazed, glued to astent or integrally formed at any point, for example, by etching. Thenumber of barbs is variable. In one embodiment, barbs 230 may extendfrom the self-expanding stent 208 to engage the ascending aorta arterialwall when deployed, and additional barbs may extend from theballoon-expandable stent 204 to engage the coronary sinus. Aortic stentgrafts can be used with and without barbs. In the event barbs areomitted, the stents may be configured so that the radial forces exertedupon the coronary sinus and the ascending aorta are enough to hold theballoon-expandable stent 204 and self-expanding stent 208 in place,respectively.

Referring to FIGS. 8 and 9, the arrow indicates outward deflection of anexemplary barb 230. Point A indicates the apex of the barb 230; points Band C indicate points of attachment of the barb 230 to the stent. As thestent expands upon deployment, ΔAC would have to exceed ΔAB, if the barb230 were to remain in the plane of the stent. However, the stentmaterial can neither stretch nor conform much. The disparity is resolvedby the apex A of the barb 230 moving outwards and downwards, asindicated by the arrows in FIGS. 9 and 10.

In the absence of the balloon, the barb 230 might move into the lumen ofthe stent. To be sure it moves as planned, the barb 230 can be made sothat it starts with a slight outward deflection, as shown in FIGS. 8-11.A sharp apex could be made to function as a barb, especially for a veryshort stent. In this embodiment, the initial bend is even moreimportant; otherwise, the sharp point can puncture the balloon. In apreferred embodiment, as illustrated in FIG. 11, a stent has barbs 230pointing out from each apex in an expanded state.

As noted above, the aortic stent graft 202 preferably includes anartificial valve 210. The purpose of this artificial valve 210 is toreplace the function of the recipient's native damaged or poorlyperforming aortic valve. The artificial valve 210 is preferably locatedat the distal end of the conduit 206, farther from the heart. In oneexample, the artificial valve 210 can be coupled to the conduit 206 withsuture.

The artificial valve 210 preferably includes one or more leaflets.Indeed a tubular conduit, sutured longitudinally to opposite sides ofthe neck of the self-expanding stent 208 would function as a bicuspidvalve. Alternatively, three suture lines would create a tricuspid valvewith less redundancy. Preferably, and as shown in FIGS. 2-4, theartificial valve 210 includes three leaflets. The leaflets are arrangedin the prosthesis such that the leaflets mimic a naturally occurringaortic valve. The artificial valve 210 “opens” to allow blood flow whenthe pressure on the proximal side of the artificial valve 210 is greaterthan pressure on the distal side of the artificial valve. Thus, theartificial valve 210 regulates the unidirectional flow of fluid from theheart into the aorta.

The leaflets of the artificial valve 210 can be fabricated from any atleast substantially biocompatible material including such materials aspolyester fabrics, polytetrafluoroethylene (PTFE), expanded PTFE, andother synthetic materials known to those of skill in the art.Preferably, the leaflets are fabricated from naturally occurringbiomaterials. The leaflets can include a derived collagen material, suchas an extracellular matrix. The extracellular matrix can be smallintestinal submucosa, stomach submucosa, pericardium, liver basementmembrane, urinary bladder submucosa, tissue mucosa, dura mater, or thelike.

The normal, native aortic valve is suspended from above through itsattachment to the walls of the coronary sinus in between the coronaryorifices, and it has leaflets of the perfect size and shape to fill thespace in the annulus. While suspended valves resist the forces createdby diastolic pressure on closed leaflets through attachment todownstream support, it is also possible to support the membrane“leaflets” of an artificial valve from below, just as the struts of amodern tent support the fabric. This approach is described below and hasparticular advantages in sites where the base of the valve is wide andsuitable sites for downstream anchoring are few.

Various artificial valve designs may be used. These designs preferablyhave at least two membranes with overlapping holes/slits/flaps so thatthere is no direct path from one side to the other. In the phase of flow(systole for the aortic valve, diastole for the mitral) the membraneslift from the underlying supports, separate and allow blood to escapethrough their holes. This works best if the outer membrane(s) isslightly baggier than the inner membrane(s). A wide variety of slots andflaps is possible.

In the example shown in FIG. 12, the inner membrane has a central hole250 and the outer membrane has a series of peripheral slits 260 thatallow for passage of fluid. In some embodiments, the slits 260 can bealmost the whole area of the outer part so that the intervening fabricis just a series of radial tethers. FIG. 12 illustrates the operation ofsuch an artificial valve, during A) diastole, and B) systole. The arrowsin FIG. 12B indicate the direction of blood flow through the slits andthus through the valve during systole.

The artificial valve flap need not be a floppy membrane; it could havesome rigidity to better support itself in the presence of a rudimentaryperipheral attachment mechanism. A single disc could be formed in situfrom a spiral ribbon, like a flattened out watch spring. If the wholevalve were conical it would transmit the longitudinal forces generatedby the pressure gradient of diastole to its edges, where a robust stentwould secure the mechanism to the annulus. Separation of the coilslayers would allow flow in systole.

In some embodiments, the anchoring/support framework for the artificialvalve 210 can take a number of shapes, such as cylinder, flattened ball,doughnut, double disc, etc., as illustrated in part in FIGS. 13-15. Ofall these, the doughnut may provide more support through tensioning thevalve membrane than by direct contact with the membrane's underside.Shown in FIG. 13 is an example of a mesh ball or doughnut, illustratingthe positioning of an outer membrane 270, an inner membrane 272, andradial slots 274.

The double disc version, shown in FIG. 14, could be made with acompletely impervious covering (no slits or holes), to serve not as avalve but as a baffle or barrier. Indeed, one side of the valve could bethinner than the other to close off some intravascular space. The thinside would sit outside the space and present a smooth, flush surface.The thick side would sit within the space and fill it up, while alsoproviding stability.

Illustrated in FIG. 14 are the valve membranes 280, and the position ofthe native aortic valve 282. The direction of blood flow is indicatedwith an arrow 284. The mesh ball valve designs, such as the design shownin FIG. 14, might benefit from having the wires of the weave start andend at the margins of the disc. They would tend to spike the surroundingtissue (or in the case of the double disc, the intervening tissue) andsecure the mesh in place.

In general, the supportive frame need not only be a mesh ball or a disc.In some embodiments, the membrane could be conical (tent shaped), e.g.similar to an over-the-wire Greenfield® filter, as shown in FIG. 15.Illustrated in FIG. 15 are the valve membranes 292, the umbrella frame294, and one or more attachment hooks 296.

The aortic stent graft is introduced into a recipient's vascular system,delivered, and deployed using a deployment device, or introducer. Thedeployment device delivers and deploys the aortic stent graft within theaorta at a location to replace the aortic valve, as shown in FIGS. 5 and6. The deployment device may be configured and sized for endoluminaldelivery and deployment through a femoral cut-down. Typically, thedeployment device includes a cannula or a catheter, capable of having avariety of shapes. The aortic stent graft may be radially collapsed andinserted into the catheter or cannula using conventional methods. Inaddition to the cannula or catheter, various other components may needto be provided in order to obtain a delivery and deployment system thatis optimally suited for its intended purpose. These include and are notlimited to various outer sheaths, pushers, stoppers, guidewires,sensors, etc.

Examples of delivery systems for endoluminal devices are known in theart. U.S. Patent Application Publication No. US 2003/0149467 A1“Methods, Systems and Devices for Delivering Stents” provides examplesof available stent delivery systems. Another example of a system andmethod of delivering endovascular devices was previously described inU.S. Pat. No. 6,695,875 “Endovascular Stent Graft.” PCT PatentPublication No. WO98/53761 “A Prosthesis and a Method of Deploying aProsthesis” discloses an introducer for a prosthesis that retains theprosthesis so that each end can be moved independently. As well, theZenith® TAA Endovascular Graft uses a delivery system that iscommercially available from Cook Inc., Bloomington, Ind.

In one aspect, a trigger wire release mechanism is provided forreleasing a retained end of a stent graft and includes a stent graftretaining device, a trigger wire coupling the stent graft to the stentgraft retaining device, and a control member for decoupling the triggerwire from the stent graft retaining device. Preferably the trigger wirearrangement includes at least one trigger wire extending from a releasemechanism through the deployment device, and the trigger wire is engagedwith the proximal end of the aortic stent graft. In a preferredembodiment where the aortic stent graft is modular and includes multipleportions, there can be multiple trigger wires extending from the releasemechanism through the deployment device, each of the trigger wiresengaging with at least one portion of the aortic stent graft.Preferably, the aortic stent graft includes three members(balloon-expandable stent, conduit, and self-expanding stent). Thus, inone preferred embodiment, three trigger wires individually engage eachof these three members of the prosthesis. Individual control of thedeployment of each of the members of the prosthesis enables bettercontrol of the deployment of the prosthesis as a whole.

FIG. 16 shows an exemplary introducer that may be used to deploy theaortic stent graft described above. The introducer is used for deployingan aortic stent graft 202 in an arterial lumen of a patient during amedical procedure. The introducer includes an external manipulationsection 301, and a proximal positioning mechanism or attachment region302. The introducer can also have a distal positioning mechanism orattachment region 303. During a medical procedure to deploy the aorticstent graft, the proximal and distal attachment regions 302 and 303 willtravel through the arterial lumen to a desired deployment site. Theexternal manipulation section 301, which is acted upon by a user tomanipulate the introducer, remains outside of the patient throughout theprocedure.

As illustrated in FIG. 16, the aortic stent graft 202 is retained in acompressed condition by a sheath 330. The sheath 330 can radiallycompress the aortic stent graft 202 over a distal portion of a thinwalled tube 315. The thin walled tube 315 is generally flexible and mayinclude metal. A tube 341, which can be made of plastic, is coaxial withand radially outside the thin walled tube 315. The distal end of thetube 341 is adjacent to the proximal end of the aortic stent graft 202.The tube 341 acts as a pusher to release the stent graft 202 from theintroducer during delivery.

The tube 341 is “thick walled”, which is to say the thickness of thewall of tube 341 is several times that of the thin walled tube 315.Preferably, the tube 341 is five or more times thicker than the thinwalled tube 315. The sheath 330 is coaxial with and is positionedradially outside the thick walled tube 341. The thick walled tube 341and the sheath 330 extend proximally to the external manipulation region301, as shown in FIG. 16. The thin walled tube 315 extends to theproximal end of the introducer. The introducer further includeshaemostatic sealing means 331 radially disposed about the sheath and thethick walled tube 341. The haemostatic sealing means 331 control theloss of blood through the introducer during a procedure.

The introducer may include an aortic stent graft control member 381 asillustrated in FIG. 16. The stent graft control member 381 is disposedon the dilator portion 334 of the external manipulation section 301.During deployment of the aortic stent graft 202, the sheath 330 iswithdrawn proximally over the thick walled tube 341. The haemostaticsealing means 331 generally fits tightly about the sheath 330, resultingin a great amount of friction between the sheath 330 and the thickwalled tube 341. As a result, withdrawal of the sheath 330 over thethick walled tube 341 can be difficult. In order to overcome thefriction, the operator must have a very tight grip on the thick walledtube 341. Axial positioning of the aortic stent graft 202 may becompromised by the difficulty in gripping the thick walled tube 341. Thecontrol member 381 solves this problem by providing the operator with abetter grip on the dilator and by decreasing the force that the operatormust exert to control and stabilize the thick walled tube 341 duringsheath 330 withdrawal. The control member 381 is generally tubular andincludes an inner dilator facing surface 382 and an outer grip surface383. The control member 381 is slidably disposed on the thick walledtube 341 between the haemostatic sealing means 331 and the release wireactuation section to allow the operator to use the control member 381 atany position along the dilator.

The outer grip surface 383 is adapted so that the control member 381fits the operator's hand comfortably and securely. As such, the outergrip surface 383 may have a diameter that greatly exceeds the diameterof the thick walled tube 341. The outer grip surface 383 may begenerally axially uniform. Alternately, the outer grip surface 383 maybe generally axially non-uniform, resulting in a contoured grippingsurface. FIG. 16 illustrates a control member 381 having a generallynon-uniform outer grip surface 383, wherein the control member isgenerally shaped like an hour glass. The outer grip surface 383 mayinclude a smooth surface finish, or alternately, the outer grip surfacemay include a rough or textured surface finish. Rough or texturedsurface finishes are beneficial because they provide increased surfacearea contact between the operator and the control member 381, therebyincreasing the operator's leverage. Multiple surface finishes may beselected to provide various utilitarian and tactile benefits.

The control member 381 is generally deformable so that when the operatorgrips the control member 381, the control member 381 compresses againstthe thick walled tube 341. The control member 381 transfers the forceexerted by the operator to the thick walled tube 341. The dilator facingsurface 382 may include a generally smooth surface. Alternately, thedilator facing surface 382 may have a rough or textured surface. A roughor textured surface may create a more “sticky” or “tacky” contactbetween the control member 381 and the thick walled tube 341, therebyincreasing the force that is transferred by the operator to the dilator.

The dilator facing surface 382 may include a generally uniform surface.Alternately, the dilator facing surface 382 may include a generallynon-uniform surface. For example, the dilator gripping surface 382 mayinclude a plurality of engageable projections that extend radiallyinward towards the thick walled tube 341. When the operator grips thecontrol member 381 against the thick walled tube 341, engageableprojections engage the surface of the thick walled tube. Engageableprojections increase the surface contact area between the control member381 and the thick walled tube, thereby increasing the force that thecontrol member transfers from the operator to the thick walled tube 341.Engageable projections may include any geometric or non-geometric shape.For example, engageable projections may include “O” shapes, lines,dashes, “V” shapes, or the like.

The distal attachment region 303 includes a retention device 310. Theretention device 310 holds the distal end of the aortic stent graft in acompressed state. The retention device 310 has at its distal end a longtapered flexible extension 311. The flexible extension 311 includes aninternal longitudinal aperture which facilitates advancement of thetapered flexible extension 311 along a previously inserted guidewire.The longitudinal aperture also provides a channel for the introductionof medical reagents. For example, it may be desirable to supply acontrast agent to allow angiography to be performed during placement anddeployment phases of the medical procedure.

The distal end of the thin walled tube 315 is coupled to the flexibleextension 311. The thin walled tube 315 is flexible so that theintroducer can be easily advanced. The thin walled tube extendsproximally through the introducer to the manipulation section 301,terminating at a connection means 316. The thin walled tube 315 is inmechanical communication with the flexible extension, allowing theoperator to axially and rotationally manipulate the distal attachmentregion 303 with respect to the aortic stent graft 202. The connectionmeans 316 is adapted to accept a syringe to facilitate the introductionof reagents into the thin walled tube 315. The thin walled tube 315 isin fluid communication with the flexible extension 311, which providesfor introduction of reagents through the aperture into the arteriallumen.

The trigger wire release actuation section of the external manipulationsection 301 includes an elongate body 336. Distal and proximal triggerwire release mechanisms 324, 325 are disposed on the elongate body 336.End caps 338 are disposed on proximal and distal ends of the elongatebody 336. End caps 338 include longitudinally-facing laterally opposedsurfaces defining distal and proximal stops 388, 389. Distal andproximal trigger wire release mechanisms 324, 325 are slidably disposedon the elongate body 336 between distal and proximal stops 388, 389.Distal and proximal stops 388, 389 retain the distal and proximaltrigger wire release mechanisms 324, 325 on the elongate body 336. Theactuation section includes a locking mechanism for limiting the axialdisplacement of trigger wire release mechanisms 324, 325 on the elongatebody 336.

Referring to the external manipulation section 301, a pin vise 339 ismounted onto the proximal end of the elongate body 336. The pin vise 339has a screw cap 346. When screwed in, the vise jaws clamp against(engage) the thin walled metal tube 315. When the vise jaws are engaged,the thin walled tube 315 can only move with the body 336, and hence thethin walled tube 315 can only move with the thick walled tube 341. Withthe screw cap 346 tightened, the entire assembly can be moved as onewith respect to the sheath 330.

The self-expanding stent 208 causes the aortic stent graft 202 to expandduring its release from the introducer 301, shown in FIG. 16. The stentgraft shown in this example also includes barbs 230 that extend from thedistal end of the self-expanding stent 208. When the self-expandingstent 208 is deployed (released), the barbs 230 anchor the distal end ofthe aortic stent graft 202 to the surrounding lumen (not shown). Uponendoluminal deployment, the balloon-expandable stent 204 is inflated andexpanded. Expansion of the balloon-expandable stent can be caused byinflation of the catheter between the sleeves so that the ends of thestent are withdrawn from the respective sleeves and the stent releasedand expanded into position. The tubular conduit 206 is also expandedupon release from the introducer. When the tubular conduit 206 ispositioned between the balloon-expandable stent 204 and theself-expanding stent 208 and is in contact with those two stents,expansion of those two stents 204 and 208 results in expansion of thetubular conduit 206 as well. Preferably, the tubular conduit 206 is thinwalled, which aids in its expansion when released.

While various embodiments of the invention have been described, theinvention is not to be restricted except in light of the attached claimsand their equivalents. Moreover, the advantages described herein are notnecessarily the only advantages of the invention and it is notnecessarily expected that every embodiment of the invention will achieveall of the advantages described.

1. An endoluminal prosthesis comprising: a first stent; a tubularconduit comprising an aortic valve replacement, wherein at least aportion of the tubular conduit overlaps at least a portion of the firststent; and a second stent that overlaps at least a portion of thetubular conduit, wherein ones of the first stent, the tubular conduit,and the second stent are coaxially arranged for unidirectionally passingfluid through the prosthesis.
 2. The endoluminal prosthesis of claim 1,wherein the first stent comprises a balloon-expandable stent and thesecond stent comprises a self-expanding stent.
 3. The endoluminalprosthesis of claim 2, wherein the self-expanding stent at leastpartially surrounds the tubular conduit, and the tubular conduit atleast partially surrounds the balloon-expandable stent.
 4. Theendoluminal prosthesis of claim 2, wherein both the balloon-expandablestent and the self-expanding stent at least partially surround thetubular conduit.
 5. The endoluminal prosthesis of claim 1, wherein theaortic valve replacement comprises an artificial valve.
 6. Theendoluminal prosthesis of claim 1, wherein the aortic valve replacementis located at the distal end of the tubular conduit.
 7. The endoluminalprosthesis of claim 1 further comprising one or more barbs.
 8. Theendoluminal prosthesis of claim 1, wherein at least one of the firststent or the second stent comprises a braided bottle stent.
 9. Aprosthesis for replacing an aortic valve comprising: at least first,second and third tubular members, wherein one of the first, second orthird tubular members comprises a valve, and wherein ones of the firsttubular member, the second tubular member, and the third tubular memberare coaxially arranged for unidirectionally passing fluid through theprosthesis.
 10. The prosthesis of claim 9, wherein at least one of thefirst, second and third tubular members comprises a balloon-expandablestent.
 11. The prosthesis of claim 9, wherein at least one of the first,second and third tubular members comprises a braided bottle stent. 12.The prosthesis of claim 9, wherein at least one of the first, second andthird tubular members comprises a self-expanding stent.
 13. Theprosthesis of claim 9, wherein the second tubular member comprises atubular conduit, wherein the valve is located at a distal end of thetubular conduit.
 14. The prosthesis of claim 9 further comprising one ormore barbs.
 15. A method of replacing an aortic valve in a subject, themethod comprising: introducing into a vascular system an endoluminalprosthesis comprising a first stent, a tubular conduit comprising avalve, and a second stent, wherein at least a portion of the tubularconduit overlaps at least a portion of the first stent, and at least aportion of the tubular conduit overlaps at least a portion of the secondstent; advancing the endoluminal prosthesis within the vascular systemtowards an aortic annulus; and expanding at least a portion of theprosthesis into engagement with the aortic annulus.
 16. The method ofclaim 15 wherein the first stent comprises a balloon expandable stentand the second stent comprises a self-expanding stent, the methodfurther comprising introducing the balloon expandable stent, the tubularconduit, and the self-expanding stent into the vascular system in asequential manner.
 17. The method of claim 15 wherein the first stentcomprises a balloon expandable stent and the second stent comprises aself-expanding stent, the method further comprising introducing theballoon expandable stent, the tubular conduit, and the self-expandingstent into the vascular system simultaneously.
 18. The method of claim15 wherein the first stent, the tubular conduit and the second stent areprovided for unidirectionally passing fluid through the prosthesis andat least inhibiting retrograde flow through the prosthesis.
 19. Themethod of claim 15 further comprising expanding the first stent intoengagement with the aortic annulus.
 20. The method of claim 15 furthercomprising positioning the second stent in the subject's ascendingaorta.